What does parasite mean?
A parasite is an organism that lives on or inside another organism, called the host, and obtains nourishment or shelter from it. The relationship often harms the host: fleas, ticks, lice, tapeworms, and many microorganisms are familiar examples. Parasites may live on the surface of a host or within its tissues, and they can affect animals, plants, or humans. The word also has a strongly negative figurative meaning. A social or financial parasite is someone who depends on another person while giving little or nothing in return, often despite having the ability to contribute. This figurative sense is a common subject of moral and political criticism, so it can sound especially severe. The term comes from ancient Greek, where parasitos referred literally to someone who ate beside another. Its long history reflects both the biological prevalence of parasitic relationships and the longstanding human concern with those who take more than they give.
An organism that lives on or in another organism, obtaining nourishment or shelter from it and often harming it; figuratively, a person who exploits another person's resources.
"The parasite attached itself to the animal's fur and fed on its blood."
The figurative sense is derogatory and usually implies a one-sided relationship in which the person benefits while the other is exploited.
To behave as a parasite by living at another person's expense or exploiting their hospitality.
"He refused to parasite on friends who had already supported him too often."
This verb is uncommon and more often encountered in literary, political, or figurative contexts than in neutral daily speech.
The plural is used for parasitic organisms and, figuratively, for people who exploit others.
"The veterinarian prescribed treatment for the parasites found in the dog."
From the Greek for someone who eats beside another, a parasite has been a fellow diner—and an uninvited guest—ever since.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does parasite come from?
The English word comes through Latin parasitus from Greek parasitos, a term for a person who eats beside another. The Greek formation is commonly connected with para, meaning beside, and sitos, meaning food or grain. In ancient usage it could refer to a guest who shared a meal and, eventually, to someone who benefited at another's expense. English adopted the word in the 16th century, and it was later applied in biology to organisms living on or in a host.
Related word forms
How parasite is actually used
The figurative use is strongly derogatory and describes someone who exploits another person's generosity, hospitality, or resources. In biology, parasitism usually implies harm to the host, although some host-parasite relationships are less harmful than others.
Easily confused with parasite
A parasite is the organism or person that benefits from another; parasitic is the adjective describing that behavior or relationship.
A parasite generally remains associated with its living host, whereas a parasitoid eventually kills its host.